Radioactive Hot Springs in Japan

I wasn't aware of this but Japan actually has many onsens (hot springs) that are naturally radioactive and well-known for it.  In fact Japan has something of a reputation for them.  They are visited by locals and tourists for their supposedly health-inducing and even cancer-preventative properties.  The most common source of the radioactivity is radon, a naturally occurring element that results from the breakdown of uranium or thorium. 

 Here's an ad for Misasa Hot Springs, which promotes its 'health-promoting radium', and a newspaper article about the cancer-fighting action of the radiation at Yawaragi onsen, located, ironically enough, in the mountains of Fukushima.  Wouldn't it be extraordinary if nearby residents had been suddenly evacuated from there because of something they had been enjoying for generations?

Radiation levels at these onsens are certainly low, low enough for radiation hormesis (if it exists) to be responsible for the health benefits, but they certainly raise eyebrows when compared to the kind of radiation that has caused widespread fear since March 11.  According to wikipedia, these kind of hot springs must have a concentration of a minimum of 74 Bq/cubic meter to qualify, and certain hot springs in Italy have concentrations of 4,000 kBq/cubic meter, while I found one Japanese site that states that Masatomi hot spring has a radiation level of 11,000 Bq/liter, and people bathe there and even drink the water for their health.  Those kinds of figures tend to put into perspective the panic that resulted when radiation levels in contaminated beef topped 500 Bq/kilogram. 

I even came across this by accident last week while on holiday in Kagoshima:

"This leg bath is a radon onsen.  For the full body bath please come inside the onsen building."

Where plenty of families (including my own) were happily bathing.

At first I found it odd that there has been no mention of these onsens in the media the last few months.  Upon reflection, it was not surprising, because the media would suffer a kind of cognitive dissonance if forced to confront the contradictions inherent in such coverage.  On one hand the public is encouraged to panic when levels of radiation are over 500 Bq/kilo of beef, but on the other hand people are known to bathe in and drink water that is much much more radioactive than that - for their health...

I wonder how many people in Japan visit their local onsen weekly, unknowingly or uncaringly luxuriating in significant levels of radon-induced radiation, only to fearfully cringe away from Fukushima produce at the supermarket